For years, parents have been limited to traditional methods of keeping track of their children's movements: standing in the playground, watching from the window, or asking them to phone home when they visit a friend's house. But now anxious mothers and fathers are being offered a distinctly hi-tech method of monitoring their child's every movement - tracking them by satellite.

Launched this week at the Consumer Electronics Show (CES) in Las Vegas, the Num8 watch from British company Lok8u is said to be the first tracking device specifically designed to help parents keep tabs on wayward offspring.

The £149 Num8 looks much like any ordinary digital wristwatch, but it houses a GPS chip similar to that contained inside a satnav unit. This constantly keeps tabs on the location of the child - it is accurate to within 3 metres - and beams it back to Num8's website for monitoring.

Relatives can receive text messages about the watch's location direct from the device, pinpointing the street address of their youngster at the touch of a button.

"As far as the child is concerned it's a digital watch - for the parent it's a child locating product," said Steve Salmon, Lok8u's chief executive. He added that he hoped it would be used as a way to give children more freedom, rather than restricting them or promoting lazy parenting.

"Only 20% of children are now allowed to go out and play. It's my profound hope that Num8 will help parents feel more comfortable about letting their children go out to play," he said.

It is not the first time that a company has offered parents the chance to track their children by GPS, but most previous devices have been built into mobile phones - expensive pieces of technology that are notoriously easy to dispense with. By contrast, Worcestershire-based Lok8u says it has improved the situation by locking the watch on to the child's wrist.

If an errant child forcibly removes the watch - or has it taken from them - the system immediately trips an alarm, sending an alert to the mobile phone of a parent. Removing the gadget also triggers a warning that is sent by email, just in case the worried parent happens to be sitting in front of a computer.

And to get around the limitations of satellite tracking technology - such as going indoors to prevent the satellite overhead from establishing a direct connection - the system can also use mobile phone signal triangulation to determine a more approximate location for its target.

The gadget was just one of thousands on display at the CES in Las Vegas, one of the world's biggest technology showcases. The event, which finished yesterday, saw more than 2,500 companies exhibit their latest gadgets and technologies - many of them targeted at children and families.